The present invention is directed to a termination for an RF circuit, and, more particularly, to a termination for an RF circuit which senses changes in power.
The detection of RF power is a common requirement for many systems. The presence and level of an RF signal may be used to indicate a failure, a query or a performance metric. Many circuits have been designed that function as power detectors using both active and passive devices. Semiconductor devices such as diodes, have been used to detect power. However, such semiconductor devices have many problems. Among these problems are that the devices are generally not linear, they are temperature sensitive, are subject to being adversely affected by static discharge, have limited frequency range and are generally expensive. Passive devices, such as bolometers and thermocouples, have also been used, but also have many problems. They generally require additional circuitry to provide the determination of the power so that they are expensive. Also, it would be desirable to have a relatively inexpensive device which can determine changes in power of an RF circuit and also will act as a termination for the circuit.
A power detector for an RF circuit includes an RF input terminal, and first and second temperature sensitive resistors connected in parallel to the input termination so that the temperature sensitive resistors have a common connection to the input terminal. Preferably, the first temperature sensitive resistor has a positive temperature coefficient of resistance and the second temperature sensitive resistor has a negative temperature coefficient of resistance. Output terminals and calibration circuitry are connected to the temperature sensitive resistors.